1. Field of the Invention
The present invention is directed in general to field of wireless communication devices. In one aspect, the present invention relates to a signal processing in a wireless communication system, apparatus, and method for enabling efficient operation of power amplifiers by reducing peak to average amplitude ratios of communication signals.
2. Description of the Related Art
Wireless communication devices, such as mobile devices and base stations, typically include transmitter and receiver circuits (i.e., transceivers) in which power amplifiers are used to amplify a signal before wireless transmission to another device. For example, base stations employing wideband digital communication transmitters will constructively add a plurality of carrier signals, resulting in multi-carrier signals with large peak-to-average power ratios (PAPR) which can adversely constrain the performance of high power amplifiers used to amplify the multi-carrier signal for a transmission. Such high power amplifiers can be very expensive and inefficient parts of the base stations, in part, because the power amplifiers are designed according to the maximum peak power that they have to handle. In order to reduce the cost and improve efficiency of the power amplifier, crest factor reduction (CFR) algorithms have been developed to reduce the peak power of the signals that the power amplifier must amplify. Typically, CFR processing is applied in real time to sequentially process input signal samples to detect peaks in the signal envelope above a certain threshold, and then perform subtractive modification of a region surrounding each detected peak to suppress the peaks to below the threshold. Such real-time detection and processing to sequentially suppress peaks one at a time can impose significant complexity and costs in requiring specialized hardware (such as delay units, synchronization circuits, etc.) and/or high sampling rates, and can also be susceptible to known problems, such as peak regrowth, etc.